1. Field of the Invention
The invention relates to a method of manufacturing N-alkyl-N'-methyl-alkyleneureas, particularly N,N'-dimethyl-alkyleneureas, from the corresponding N-alkyl-N'-hydroxymethyl-alkyleneureas or N,N'-bis(hydroxymethyl)-alkyleneureas, by reaction with formic acid. Here "alkylene" means a bifunctional organic group, e.g., a 1,2-ethylene, or 1,3-propylene group. The preferred application of the method is in manufacturing N,N'-dimethyl-alkyleneureas.
The conversion noted above can be accomplished from the corresponding alkyleneureas and formaldehyde, or directly from urea and the corresponding diamine. It is unnecessary to isolate the N-alkyl-N'-hydroxymethyl-alkyleneurea or the N,N'-bis(hydroxymethyl)-alkyleneurea.
2. Discussion of the Background
There are known methods of manufacturing N,N'-dialkyl-alkyleneureas, having the following formula ##STR1## where R.sub.1 represents H or CH.sub.3, R.sub.2 represents an alkyl group with 1 to 3 carbon atoms, and n=0 or 1. These methods comprise reacting an alkylnediol with an alkylamine and carbon dioxide at 150.degree.-500.degree. C. (Japanese No. 81-50565A); or reacting the corresponding alkylated alkylenediamine with phosgene (German AS No. 11 26 392); or alkylating the corresponding alkylenethiourea and hydrolyzing (1968, J. Med. Chem., 11, 214); or reducing a functionalized precursor where R.sub.1 is alkoxy (German OS No. 15 45 613.
Practical commercial methods for converting alkyleneureas into the corresponding N,N'-dialkylalkyleneureas are not known, however. Alkyleneureas, e.g., ethyleneurea, are commercially available in industrial quantities (U.S. Pat. No. 2,497,309); and it is easy to prepare N-alkyl-N'-hydroxymethyl-alkyleneureas (or N,N'-bis(hydroxymethyl)alkyleneureas) from these alkyleneurea (U.S. Pat. No. 2,613,210). Accordingly, one faces the problem of how to convert N-alkyl-N'-hydroxymethyl-alkyleneureas or N,N'-bis(hydroxymethyl)-alkyleneureas into N-alkyl-N'-methyl-alkyleneureas or N,N'-dimethyl-alkyleneureas, respectively.